MAC: CO2 or HFO-1234yf?
The SAE Alternate Refrigerant Symposium held in Phoenix, USA, on June 10-12, 2008, provided an opportunity for the various stakeholders of the global automotive industry to present their views regarding the next-generation refrigerant in mobile air conditioning (MAC) and their test results with CO2 and HFO-1234yf, the two main options now considered to replace HFC-134a. DuPont and Honeywell, which developed R-1234yf, confirmed that flammability and toxicity test results are expected by August 2008 and that serial production could start in November 2010, just 2 months before the EU Directive deadline banning the use of R-134a in new MAC systems. The system supplier Visteon, which had found earlier that latest CO2 MAC systems would be more efficient than state-of-the-art R-134a systems, stated that R-1234yf could reach the same performance as current R-134a systems but specified that it would not be a drop-in solution and would require extra costs besides the refrigerant itself. The German Automotive Association (VDA) confirmed that German carmakers, which had already selected CO2 as the better option, were not evaluating R-1234yf. French (Renault and PSA Peugeot Citroen) and Italian (Fiat) carmakers highlighted major progress in efficiency for CO2 MAC systems but were still hesitant about a final choice for CO2. General Motors (USA) stressed that CO2 might be subject to use conditions in the US and welcomed improved seal designs avoiding CO2 leakage. It announced that the development of a new PAG oil formulation needed to be validated for R-1234yf and that a refrigerant decision would probably be made by December 2008. Representatives of Japanese and Korean carmakers confirmed a similar time-schedule for decision.